The Energizer specs suggest to me it has a single AAA rechargeable in it - they definitely weren't even trying for long runtimes. The Blackout buddy doesn't give a brightness spec, so it's hard to tell what it has.
All of the emergency lights I've seen look unimpressive, but sufficient for getting caught in a blackout with no flashlight in reach, making it easier to then go find a good flashlight.
None that I've seen appear to have anymore utility beyond that first 2-3 minutes compared to basically any other flashlight you can find.
Emergency lighting in commercial buildings mainly serves to allow you to evacuate safely, so the limited battery life arguably isn't significant. At home, I could be asleep, but wake up hours after the power goes out or I could come home after dark to an outage and in both cases have a dead emergency light. Then again, I keep a flashlight on my nightstand and one by the door, so I should be covered for both cases.
I have an old NiCad powered emergency light I don't use because it won't let you turn off the night light feature, which is a problem because of the obnoxious blue tint. However, it does one thing I think is a good idea: when in emergency mode, if unplugged / power lost, it dims to probably 1-2 lumens in order to extend the battery life. With power available, or in flashlight mode, it is more like 5-10 lumens.
Interestingly, one of the best flashlights my parents had I was growing up was their emergency light. It had an output roughly comparable to a 2-D Maglite, and pretty good runtime due to a custom NiCad pack. Very different from the emergency lights I see today.